• by Gavin O'Malley  @mp_gavin, March 4, 2009

Podcast usage among U.S. consumers will continue to rise at least through 2013, when there will be 37.6 million people downloading podcasts on a monthly basis--more than double the 2008 figure of 17.4 million--according to a report released Wednesday by research firm eMarketer.

"Today, the vast majority of the top-rated podcasts come from recognizable media entities that are using podcasts to expand their existing radio, TV, cable or satellite audiences," said Paul Verna, eMarketer senior analyst and author of the new report "Podcasting: Into the Mainstream."

U.S. buyers who purchase mostly online showed an even greater propensity to listen to podcasts, according to eMarketer. Some 50% of mostly online buyers in a PriceGrabber.com survey, for instance, said they listened to podcasts--a far greater number than comparable percentages of Internet users or consumers as a whole.

As for who is doing the downloading, a Pew Internet & American Life Project demographic profile of U.S. adult Internet users who downloaded podcasts showed that they skewed male and young.

Users ages 18 to 29 had the highest representation of podcast downloaders, while rates of podcast downloading steadily decreased for older age groups.

"The popularity of podcasts has created an environment in which increasing numbers of media companies are repurposing content from their radio or TV broadcasts as podcasts, and audiences have responded favorably," Verna said in the new report. "This shift has resulted in the evolution of podcasting from a long-tail medium to a Web 2.0 extension of popular, traditional media."